Doing THD calc

fft_meas.py

@@ -5,7 +5,11 @@ import fft
 
 class fft_meas(object):
 	"""docstring for fft_meas"""
+	# 61000-4-7 says 200ms
+	# 10-cycles for 50Hz
+	# 12-cycles for 60Hz
 	def __init__(self, fs=50e3, tn=0.2):
+
 		self.fs = fs
 		self.ts = 1/fs
 		self.tn = tn
@@ -19,25 +23,94 @@ class fft_meas(object):
 		self.b = 0
 		self.c = 0
 		self.Y_C = 0
+
+		# 61000-4-7: 3.2.3
+		# Upto the 40 Harmonic per 3.3.1 Note 2
+		# Harmonic order
+		self.Y_H = np.zeros(40)
+		# 61000-4-7: 3.2.3
+		# Upto the 40 Harmonic per 3.3.2 Note 2
+		# Grouped Harmonic order
+		self.Y_g = np.zeros(40)
+		# 61000-4-7: 3.2.2 
+		self.h = np.zeros(40)
+
+		self.THD = 0
+		self.THDG = 0
+		
+
 		self.phi = 0
-
-	def step(self, data, time, f_H1, unit):
-
-		if time - self.time > self.ts:
-			self.time = time
-			self.idx += 1
-
-			self.data[self.idx] = data
-
-			if self.idx == self.N-1:
-
-						
-				self.freq , self.a, self.b , self.c, self.Y_C, self.phi = fft.fft(x=self.data, fs=self.fs)
-
-				self.idx = -1
+		self.base_freq = 0
 
 
+	def step(self, y, base_freq, unit):
+
+		self.idx += 1
+
+		self.data[self.idx] = y
+
+		if self.idx == self.N-1:
+
+			self.freq , self.a, self.b , self.c, self.Y_C, self.phi = fft.fft(x=self.data, fs=self.fs)
 			
+			self.calc_Y_H(base_freq)
+			self.calc_THD()
+
+			self.calc_Y_g(base_freq)
+			self.calc_THDG()
+
+
+
+			self.idx = -1
+
+
+	def calc_Y_H(self, base_freq):
+		# 61000-4-7: 3.2.3
+			if np.abs(base_freq-50) < np.abs(base_freq-60):
+				self.base_freq = 50
+			else:
+				self.base_freq = 60			
+
+			if self.base_freq == 50:
+				for k in range(len(self.Y_H)):
+					self.Y_H[k] = self.Y_C[int(10*k)]
+					self.h[k] = self.freq[int(10*k)]
+			elif self.base_freq == 60:
+				for k in range(len(self.Y_H)):
+					self.Y_H[k] = self.Y_C[int(12*k)]
+					self.h[k] = self.freq[int(12*k)]
+
+	def calc_THD(self):
+		# 61000-4-7: 3.3.1
+		self.THD = 0
+		for k in range(2, len(self.Y_H)):
+			self.THD += np.power(self.Y_H[k]/self.Y_H[1],2)
+			self.THD =  np.sqrt(self.THD)
+
+	def calc_Y_g(self, base_freq):
+		# 61000-4-7: 3.2.4
+			if np.abs(base_freq-50) < np.abs(base_freq-60):
+				self.base_freq = 50
+			else:
+				self.base_freq = 60			
+
+			if self.base_freq == 50:
+				for k in range(len(self.Y_g)):
+					self.Y_g[k] = self.Y_C[int(10*k)-1] + self.Y_C[int(10*k)] + self.Y_C[int(10*k)+1]
+					self.h[k] = self.freq[int(10*k)]
+			elif self.base_freq == 60:
+				for k in range(len(self.Y_g)):
+					self.Y_g[k] = self.Y_C[int(12*k)-1] + self.Y_C[int(12*k)] + self.Y_C[int(12*k)+1]
+					self.h[k] = self.freq[int(12*k)]
+
+	def calc_THDG(self):
+		# 61000-4-7: 3.3.1
+		self.THDG = 0
+		for k in range(2, len(self.Y_H)):
+			self.THDG += np.power(self.Y_g[k]/self.Y_g[1],2)
+			self.THDG =  np.sqrt(self.THDG)
+		print(self.THDG)
+		
 	def plot(self):
 		#fs, a, b, c, YC, phi = ftt.fft(Ph1, sample_freq)
 
@@ -47,3 +120,11 @@ class fft_meas(object):
 		plt.title("Simple plot")
 		plt.show()
 		
+	def plot_Y_H(self):
+
+		plt.stem(self.h, self.Y_H, use_line_collection=True)
+		plt.xlabel("Harmonic order h")
+		plt.ylabel("RMS value Y_H,h")
+		plt.title("Harmonic spectrum (IEC 61000-4-7: 3.2.3)")
+		plt.grid(True)
+		plt.show()