dp.cpp

/* Dynamic Phasor Interface Algorithm hook.
 *
 * Author: Steffen Vogel <post@steffenvogel.de>
 * SPDX-FileCopyrightText: 2014-2023 Institute for Automation of Complex Power Systems, RWTH Aachen University
 * SPDX-License-Identifier: Apache-2.0
 */

#include <cmath>
#include <complex>
#include <cstring>

#include <villas/dsp/window.hpp>
#include <villas/hook.hpp>
#include <villas/sample.hpp>
#include <villas/utils.hpp>

using namespace std::complex_literals;
using namespace villas::utils;

namespace villas {
namespace node {

class DPHook : public Hook {

protected:
  char *signal_name;
  unsigned signal_index;

  int inverse;

  double f0;
  double timestep;
  double time;
  double steps;

  std::complex<double> *coeffs;
  int *fharmonics;
  int fharmonics_len;

  dsp::Window<double> window;

  void step(double *in, std::complex<float> *out) {
    int N = window.size();
    std::complex<double> om_k, corr;
    double newest = *in;
    __attribute__((unused)) double oldest = window.update(newest);

    for (int k = 0; k < fharmonics_len; k++) {
      om_k = 2.0i * M_PI * (double)fharmonics[k] / (double)N;

      // Correction for stationary phasor
      corr = std::exp(-om_k * (steps - (N + 1)));
      //corr = 1;

#if 0
      // Recursive update
      coeffs[k] = std::exp(om) * (coeffs[k] + (newest - oldest));

      out[k] = (2.0 / N) * (coeffs[i] * corr);

      // DC component
      if (fharmonics[k] == 0)
        out[k] /= 2.0;
#else
      // Full DFT
      std::complex<double> X_k = 0;

      for (int n = 0; n < N; n++) {
        double x_n = window[n];

        X_k += x_n * std::exp(om_k * (double)n);
      }

      out[k] = X_k / (corr * (double)N);
#endif
    }
  }

  void istep(std::complex<float> *in, double *out) {
    std::complex<double> value = 0;

    // Reconstruct the original signal
    for (int k = 0; k < fharmonics_len; k++) {
      double freq = fharmonics[k];
      // cppcheck-suppress objectIndex
      std::complex<double> coeff = in[k];
      std::complex<double> om = 2.0i * M_PI * freq * time;

      value += coeff * std::exp(om);
    }

    *out = std::real(value);
  }

public:
  DPHook(Path *p, Node *n, int fl, int prio, bool en = true)
      : Hook(p, n, fl, prio, en), signal_name(nullptr), signal_index(0),
        inverse(0), f0(50.0), timestep(50e-6), time(), steps(0), coeffs(),
        fharmonics(), fharmonics_len(0) {}

  ~DPHook() override {
    // Release memory
    if (fharmonics)
      delete fharmonics;

    if (coeffs)
      delete coeffs;

    if (signal_name)
      free(signal_name);
  }

  void start() override {
    assert(state == State::PREPARED);

    time = 0;
    steps = 0;

    for (int i = 0; i < fharmonics_len; i++)
      coeffs[i] = 0;

    window = dsp::Window<double>((1.0 / f0) / timestep, 0.0);
    if (window.size() == 0) {
      throw RuntimeError(
          "Windows size is 0: f0 * timestep < 1.0 not satisfied");
    }

    state = State::STARTED;
  }

  void parse(json_t *json) override {
    int ret;
    json_error_t err;
    json_t *json_harmonics, *json_harmonic, *json_signal;
    size_t i;

    Hook::parse(json);

    double rate = -1, dt = -1;

    ret = json_unpack_ex(json, &err, 0,
                         "{ s: o, s: F, s?: F, s?: F, s: o, s?: b }", "signal",
                         &json_signal, "f0", &f0, "dt", &dt, "rate", &rate,
                         "harmonics", &json_harmonics, "inverse", &inverse);
    if (ret)
      throw ConfigError(json, err, "node-config-hook-dp");

    if (rate > 0)
      timestep = 1. / rate;
    else if (dt > 0)
      timestep = dt;
    else
      throw ConfigError(
          json, "node-config-hook-dp",
          "Either on of the settings 'dt' or 'rate' must be given");

    if (!json_is_array(json_harmonics))
      throw ConfigError(json_harmonics, "node-config-hook-dp-harmonics",
                        "Setting 'harmonics' must be a list of integers");

    switch (json_typeof(json_signal)) {
    case JSON_STRING:
      signal_name = strdup(json_string_value(json_signal));
      break;

    case JSON_INTEGER:
      signal_name = nullptr;
      signal_index = json_integer_value(json_signal);
      break;

    default:
      throw ConfigError(json_signal, "node-config-hook-dp-signal",
                        "Invalid value for setting 'signal'");
    }

    fharmonics_len = json_array_size(json_harmonics);
    fharmonics = new int[fharmonics_len];
    coeffs = new std::complex<double>[fharmonics_len];
    if (!fharmonics || !coeffs)
      throw MemoryAllocationError();

    json_array_foreach (json_harmonics, i, json_harmonic) {
      if (!json_is_integer(json_harmonic))
        throw ConfigError(json_harmonic, "node-config-hook-dp-harmonics",
                          "Setting 'harmonics' must be a list of integers");

      fharmonics[i] = json_integer_value(json_harmonic);
    }

    state = State::PARSED;
  }

  void prepare() override {
    assert(state == State::CHECKED);

    std::string new_sig_name;

    assert(state != State::STARTED);

    if (signal_name) {
      int si = signals->getIndexByName(signal_name);
      if (si < 0) {
        throw RuntimeError("Failed to find signal: {}", signal_name);
      }
      signal_index = si;
    }

    if (inverse) {
      // Remove complex-valued coefficient signals
      for (int i = 0; i < fharmonics_len; i++) {
        auto orig_sig = signals->getByIndex(signal_index + i);
        if (!orig_sig)
          throw RuntimeError("Failed to find signal");

        if (orig_sig->type != SignalType::COMPLEX)
          throw RuntimeError("Signal is not complex");

        signals->erase(signals->begin() + signal_index + i);
      }

      // Add new real-valued reconstructed signals
      auto new_sig = std::make_shared<Signal>("dp", "idp", SignalType::FLOAT);
      if (!new_sig)
        throw RuntimeError("Failed to create signal");

      signals->insert(signals->begin() + signal_index, new_sig);
    } else {
      auto orig_sig = signals->getByIndex(signal_index);
      if (!orig_sig)
        throw RuntimeError("Failed to find signal");

      if (orig_sig->type != SignalType::FLOAT)
        throw RuntimeError("Signal is not float");

      signals->erase(signals->begin() + signal_index);

      for (int i = 0; i < fharmonics_len; i++) {
        new_sig_name = fmt::format("{}_harm{}", orig_sig->name, i);

        auto new_sig = std::make_shared<Signal>(new_sig_name, orig_sig->unit,
                                                SignalType::COMPLEX);
        if (!new_sig)
          throw RuntimeError("Failed to create new signal");

        signals->insert(signals->begin() + signal_index, new_sig);
      }
    }

    state = State::PREPARED;
  }

  void check() override {
    assert(state == State::PARSED);

    if (signal_index < 0)
      throw RuntimeError("Signal index not set");

    if (fharmonics_len <= 0)
      throw RuntimeError("No harmonics given");

    if (timestep <= 0)
      throw RuntimeError("Invalid timestep");

    if (f0 <= 0)
      throw RuntimeError("Invalid fundamental frequency");

    state = State::CHECKED;
  }

  Hook::Reason process(struct Sample *smp) override {
    if (signal_index >= smp->length)
      return Hook::Reason::ERROR;

    if (inverse) {
      double signal;
      std::complex<float> *coeffs =
          reinterpret_cast<std::complex<float> *>(&smp->data[signal_index].z);

      istep(coeffs, &signal);

      sample_data_remove(smp, signal_index, fharmonics_len);
      sample_data_insert(smp, reinterpret_cast<union SignalData *>(&signal),
                         signal_index, 1);
    } else {
      double signal = smp->data[signal_index].f;
      std::complex<float> coeffs[fharmonics_len];

      step(&signal, coeffs);

      sample_data_remove(smp, signal_index, 1);
      sample_data_insert(smp, reinterpret_cast<union SignalData *>(coeffs),
                         signal_index, fharmonics_len);
    }

    time += timestep;
    steps++;

    return Reason::OK;
  }
};

// Register hook
static char n[] = "dp";
static char d[] = "Transform to/from dynamic phasor domain";
static HookPlugin<DPHook, n, d,
                  (int)Hook::Flags::PATH | (int)Hook::Flags::NODE_READ |
                      (int)Hook::Flags::NODE_WRITE>
    p;

} // namespace node
} // namespace villas